1. Field of the Invention
This invention relates to fragmentation by the open pit method and particularly, after the ore body has been exhausted and mining operations completed, relates to putting the pit and surrounding land in condition for future usefulness, and for the satisfaction of esthetic and practical considerations.
2. Description of the Prior Art
It has been the usual custom in the past simply to abandon a worked-out open pit. It then became an eyesore and perphaps a hazard. Often the pit filled with water, children swam in it and drownings occurred. The pit area was useless to farmers and ranchers and became a waste area.
Objections have been raised to this practise of abandoning open pits after exhausting the minerals from them and governmental entities have passed laws requiring miners to put the pit and the surrounding area back in such shape that it can again be useful, safe and not an eyesore.
For example, States have passed laws that the residual pit wall, after exhaustion and prior to abandonment, must be cut down to a slope of not greater than 3 to 1 (three units horizontally and one vertically), 4 to 1 or 5 to 1. The conventional way of doing this has been by progressively cutting away the surface in lifts down to the required sloping plane. This is an expensive, time-consuming and equipment-intensive process.